1. Field of the Invention
The present invention relates to a heat roller control apparatus, and more particularly relates to a control apparatus for a heat roller for use in a laminator or the like.
2. Description of the Prior Art
FIG. 3 shows a conventional heat roller control apparatus. In FIG. 3, a reference numeral 1 denotes a heat roller, 1A denotes a member, such as a PVC card to be laminated with a thin film 1B, such as a PET film, 8a and 8b denote transfer rollers for transferring the member 1A and the thin film 1B, 2a denotes an actuator, such as a motor for rotating the heat roller 1, 2b denotes an actuator, such as a motor for rotating the transfer roller 8b, 3a and 3b denote driving circuits for driving the actuators 2a and 2b, respectively, 4 denotes a heater for heating the heat roller 1, 5 denotes a temperature detecting element, such as a thermistor for detecting a surface temperature of the heat roller 1, 6 denotes a temperature control circuit for controlling the excitation of the heater 4, 9 denotes a temperature judging circuit formed of a microprocessor, for example, for judging whether the surface temperature of the heat roller 1 is stable in a predetermined range lower than a first reference signal c1 indicating the upper limit value, but higher than a second reference signal c2 indicating the lower limit value, 10 denotes a temperature state indicator for indicating whether the surface temperature of the heat roller 1 is stable in the predetermined range, and 7a and 7b denote detecting elements, such as photosensors for detecting the presence of the member 1A, respectively.
FIG. 4 shows a diagram for explaining the surface temperature of the heat roller 1.
In FIG. 4, a reference symbol (a) denotes the first reference signal c1 indicating the upper limit value of the predetermined range, (b) denotes the second reference signal c2 indicating the lower limit value of the predetermined range, (c) denotes a temperature signal a outputted from the temperature sensing element 5, and (d) denotes a temperature judging signal e outputted from the temperature judging circuit 9. The temperature judging circuit 9 judges whether the temperature signal a outputted from the temperature detecting element 5 is in the predetermined range and maintained continuously for a predetermined setting period of time t1. Further, the temperature judging circuit 9 outputs the temperature judging signal e of low level xe2x80x9cLxe2x80x9d in case that the temperature signal a outputted from the temperature detecting element 5 is out of the predetermined range, or that the temperature signal a is in the predetermined range, but is not maintained continuously for the predetermined setting period of time t1. The temperature judging circuit 9 outputs the temperature judging signal e of high level xe2x80x9cHxe2x80x9d in case that the temperature signal a is in the predetermined range and maintained continuously for the predetermined setting period of time t1.
The actuator 2b is driven by the driving circuit 3b when the detecting element 7a detects the presence of the member 1A and the driving circuit 3b receives a first detecting signal b1 outputted from the detecting element 7a. The actuator 2b is not driven by the driving circuit 3b when the temperature judging signal e is low level xe2x80x9cLxe2x80x9d. The adhesive strength of the member 1A becomes small or the member 1A is deformed if the hot melt coating is carried out in the state that the surface temperature of the heat roller 1 is out of the predetermined range. The member 1A and the thin film 1B are transferred to the heat roller 1 by the rotation of the transfer roller 8b when the level of the temperature judging signal e is xe2x80x9cHxe2x80x9d and the actuator 2b is driven. The heat roller 1 is rotated when the actuator 2a is driven by the driving circuit 3a irrespective of the state of the temperature judging signal e or the first detecting signal b1 outputted from the detecting element 7a, so that the member 1A and the thin film 1B are held by the transfer roller 8a and the heat roller 1, and the hot melt coating is carried out while they are transferred. The actuator 2b is deenergized when the member 1A and the thin film 1B are passed through the detecting element 7b and the driving circuit 3b receives a second detecting signal b2 outputted from the detecting element 7b. 
The transfer of the member 1A is not carried out even if the presence of the member 1A is detected and the surface temperature of the heat roller 1 is in the predetermined range because the temperature judging signal e is low level xe2x80x9cLxe2x80x9d until the predetermined time t1 has been passed.
Thus, the time t1 becomes an idle time.
Accordingly, it is an object of this invention to provide a heat roller control apparatus free from the above defects.
It is another object of this invention to provide a heat roller control apparatus wherein a variation of a temperature signal outputted from a temperature detecting element is detected at a predetermined interval, and a temperature judging signal of high level is produced so that a member to be laminated with a thin film is transferred for hot melt coating, if the variation of the temperature signal is smaller than a predetermined value when the temperature signal reaches in a predetermined range.
According to a heat roller control apparatus of this invention, the idle time after a surface temperature of a heat roller has reached to the predetermined temperature range can be shortened.
A heat roller control apparatus according to the present invention is characterized by comprising a heat roller for hot melt coating a thin film on a member, a heater for heating the heat roller, temperature detecting means for detecting the surface temperature of the heat roller, temperature control means for controlling the heater according to a temperature detecting signal obtained from the temperature detecting means, and temperature judging means for producing a temperature judging signal for judging the state of the surface temperature of the heat roller according to the temperature detecting signal, wherein the temperature judging means calculates a variation of the surface temperature of the heat roller from the temperature detecting signal every predetermined time and judging the stability of the hot melt coating by the variation of the surface temperature of the heat roller when the temperature detecting signal reaches into a predetermined temperature range.
A heat roller control apparatus according to the present invention is characterized by comprising a heat roller for hot melt coating a thin film on a member, a heater for heating the heat roller, temperature detecting means for detecting the surface temperature of the heat roller, temperature control means for controlling the heater according to a temperature detecting signal obtained from the temperature detecting means, and temperature judging means for producing a temperature judging signal for judging the state of the surface temperature of the heat roller according to the temperature detecting signal, wherein the member to be attached with the thin film is transferred only when the surface temperature reaches into a predetermined temperature range and a variation of the surface temperature of the heat roller is smaller than a predetermined value.
The temperature judging means is a circuit comprising an A/D converter, three comparators, an AND gate, two registers, an oscillator, a subtracter, two frequency dividers, and two inverters.
Other object and advantages will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.